Magnetorheological Fan Clutch for Convertible Aircraft Engine
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Solution Overview
Problem
Convertible engines experience significant parasitic power loss and increased residual thrust due to the constant rotation of the bypass fan, even when thrust is not required, leading to inefficiencies in both thrust and mechanical shaft power modes.
Innovation Solution
The implementation of a magnetorheological clutch system that selectively couples and decouples the bypass fan from the low pressure turbine shaft, allowing the fan to spin freely when not generating thrust, thereby reducing drag and increasing the turn down ratio for shaft power conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the bypass fan is rigidly connected to the power output shaft and always rotates with engine operation, then the engine can operate as a turbofan to produce thrust, but significant parasitic power loss occurs when bypass airflow is not required
Solution Approach 1:
The patent applies a magnetorheological clutch to dynamically control the connection between the bypass fan and power output shaft. The clutch allows the fan to be rigidly connected during turbofan mode for thrust production, and freely rotating during turboshaft mode to minimize parasitic power loss. This dynamic coupling mechanism enables the system to adapt its mechanical connection based on operational requirements.
Solution Approach 2:
The magnetorheological clutch changes its mechanical coupling parameter based on operational mode. When activated, it provides rigid coupling for thrust operation; when deactivated, it allows free rotation to reduce drag. This parameter change enables the bypass fan to transition between coupled and uncoupled states, optimizing energy efficiency across different engine modes.
2Adaptability or versatility
If the bypass fan always rotates during engine operation, then thrust can be produced when needed, but the turn down ratio for shaft power conversion is reduced
Solution Approach 1:
The magnetorheological clutch provides dynamic control over the bypass fan rotation, enabling the system to switch between thrust-generating mode and power-conversion-optimized mode. During turboshaft operation, the clutch decouples the fan, allowing it to rotate freely without extracting power, thereby improving the turn down ratio and shaft power conversion efficiency.
Solution Approach 2:
The patent extracts the parasitic load of the bypass fan from the power output shaft during turboshaft operation by using the magnetorheological clutch to decouple them. This separation allows the fan to rotate independently without consuming engine power, thereby increasing the available shaft power for external loads and improving overall productivity.
3Adaptability or versatility
If the bypass fan rotates constantly, then the engine can provide thrust in turbofan mode, but filtration system components increase in size and pressure drop
Solution Approach 1:
The magnetorheological clutch enables dynamic control of bypass fan rotation, allowing the system to operate with the fan coupled during turbofan mode for bypass airflow generation, and uncoupled during turboshaft mode. This reduces the required capacity of filtration components since they only need to handle airflow during thrust operations, not during continuous rotation.
4Adaptability or versatility
If the bypass fan rotates continuously, then thrust production is maintained, but residual thrust levels increase requiring compensation by other aircraft systems
Solution Approach 1:
The magnetorheological clutch dynamically controls bypass fan rotation to eliminate residual thrust during turboshaft operation. By decoupling the fan from the power output shaft when thrust is not required, the system prevents the fan from generating unwanted residual thrust that would otherwise require compensation by other aircraft systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution significantly reduces parasitic power loss and increases the turn down ratio, making more engine power available for mechanical shaft power, with the bypass fan only rotating and generating thrust when necessary, thus enhancing overall engine efficiency.
Implementation Method 1
The fan clutch comprises a magnetorheological clutch and carries a magnetorheological fluid. A magnetic field is applied to the magnetorheological fluid to couple the bypass fan to the low pressure turbine shaft.
Data Source
AI summary
Systems and methods include providing an aircraft with a fuselage and a convertible engine disposed within the fuselage. The convertible engine is operable as a turbofan engine in a thrust mode and a turboshaft engine in a shaft power mode. The convertible engine includes a housing, an engine core having a low pressure turbine shaft, and a bypass fan system. The bypass fan system includes a bypass fan having a fan clutch. The fan clutch selectively couples at least a portion of the bypass fan to the low pressure turbine shaft when the convertible engine is operated in the thrust mode and decouples at least a portion of the bypass fan from the low pressure turbine shaft when the convertible engine is operated in the shaft power mode.